The study looked at 1,400 pairs of young adult twins in Norway, which has a much lower rate of drug use than many other countries.

"Prior twin studies of illicit drug use and abuse have all been conducted in Anglophonic countries, specifically the United States and Australia, with high levels of such use," (...) "This is the first study of a non-English speaking country with much lower rates of drug use -- yet results are similar -- drug use and abuse or dependence is quite heritable," Kendler said.

He noted the findings of this new study contradict previous theories suggesting that genetic factors may have less of an impact in societies where illicit drugs are not widely available.

I'd have to read the medical journal that the study was in to make a more informed opinion, though it would hardly surprise me to see those kinds of findings. The trick is finding enough identical twins who were separated at birth and are not living in the same environment to make this kind of study really work.
Journalists also have a tendency to pick and choose the parts of the study that they think will have the most impact (and therefore sell more papers/gain more viewers). Part of that can be lack of understanding of the technical details, though I've seen any number of journalists who had mastered a lot of medical knowledge. Part of it's because most journal articles are so darned boring, and journalists want to pick the things that keep readers' interests. Most people don't give a hoot about the amount of cyclic GMP a cell has, but do care about aspirin decreasing heart attack risks and other more practical things.

From MST3K's spoof of "Hercules Unchained"--heard as Roman medic soldiers carry off an unconscious Greek Hercules on a 1950's Army green canvas stretcher: "Hi, we're IX-I-I. Did somebody dial IX-I-I?"